3D-Printing to Plan Complex Transcatheter Paravalvular Leaks Closure

Aortic Valve Engineering Advancements: Precision Tuning with Laser Sintering Additive Manufacturing of TPU/TPE Submillimeter Membranes

Synthetic biomaterials play a crucial role in developing tissue-engineered heart valves (TEHVs) due to their versatile mechanical properties. Achieving the right balance between mechanical strength and manufacturability is essential. Thermoplastic polyurethanes (TPUs) and elastomers (TPEs) garner significant attention for TEHV applications due to their notable stability, fatigue resistance, and customizable properties such as shear strength and elasticity. This study explores the additive manufacturing technique of selective laser sintering (SLS) for TPUs and TPEs to optimize process parameters to balance flexibility and strength, mimicking aortic valve tissue properties. Additionally, it aims to assess the feasibility of printing aortic valve models with submillimeter membranes. The results demonstrate that the SLS-TPU/TPE technique can produce micrometric valve structures with soft shape memory properties, resembling aortic tissue in strength, flexibility, and fineness. These models show promise for surgical training and manipulation, display intriguing echogenicity properties, and can potentially be personalized to shape biocompatible valve substitutes.

Design and preparation of an electromechanical implant prototype for an on-demand drug delivery

INTRODUCTION

A bio-implant is a drug-delivery system that is implanted in the human body for a period of more than 30 days. Electromechanical systems are one type of bio-implant that has recently been introduced as a new generation of targeted drug delivery methods. The overarching goal of utilizing these systems is to integrate electrical and mechanical features in order to benefit from the numerous applications of these two systems when used together. The current study aimed to design a prototype of an electromechanical system using Fused Deposition Modeling (FDM), Selective Laser Sintering (SLS), and MultiJet Fusion (MJF) techniques for drug delivery that can release a specific drug dosage in the patient's body by connecting to a sensor or under the control of a signal sent by the physician.

METHODS

Initially, the implant chambers were created in the form of a hollow cylinder, closed at one end, using three different types of 3D printers: FDM, SLS, and MJF. Each implant was then filled with a model drug (pentoxifylline) and sealed with a thin gold membrane. To achieve the lowest voltage required to melt the gold membrane, an electric circuit with controllable DC voltage generator was designed. Finally, the mechanical resistance, drug release rate, and surface morphology of the designed implants were evaluated.

RESULTS

The MJF 3D printer, overally, had higher printing precision and repeatability than other printers; however, the implants printed by the FDM 3D printer were more accurate than other techniques (P value < 0.001), similar to the dimensions of the designed file. The mechanical resistance of the implants was also evaluated, and the polylactic acid implants printed by FDM had the highest value of Young's modulus in both the standard samples and the designed implants. During the 3-month drug leakage study, FDM 3D printed implant had a greater ability to store the desired drug load (P value < 0.001), Furthermore, the SEM micrographs revealed that the polylactic acid implants printed by FDM had minimal porosity in their structure and the layers were well adhered together. The gold membrane with a middle diameter of 2 mm required the lowest voltage of 6 V. As a result, the final electrical circuit was designed with smaller dimensions in order to achieve the voltage required to melt the gold membrane.

CONCLUSION

Due to the lack of drug leakage and other mechanical studies, the electromechanical implant produced by the FDM 3D printer was chosen as the optimal electromechanical implant in this study. Along with the designed small circuit, this implant can release a drug dosage in the patient's body at the physician's demand.

3D printing from transesophageal echocardiography for planning mitral paravalvular leak closure - feasibility study

Introduction

Transcatheter closure of paravalvular leak (PVL) is still a demanding procedure due to the complex anatomy of PVL channels and risk of interference between the implanted occluder and surrounding structures. Efforts are made to improve procedural outcomes in transcatheter structural heart interventions by establishing treatment strategy in advance with the use of 3D-printed physical models based on data obtained from cardiac computed tomography (CT) studies.

Aim

In this feasibility study 3D printing of PVL models based on data recorded during transesophageal echocardiography (TEE) examinations was evaluated.

Material and methods

3D-TEE data of patients with significant PVL around mitral valve prostheses were used to prepare 3D models. QLab software was used to export DICOM images in Cartesian DICOM format of each PVL with the surrounding tissue. Image segmentation was performed in Slicer, a free, open-source software package used for imaging research. Models were printed to actual size with the Polyjet printer with a transparent, rigid material. We measured dimensions of PVLs both in TEE recordings and printed 3D models. The results were correlated with sizes of occluding devices used to close the defects.

Results

In 7 out of 8 patients, there was concordance between procedurally implanted occluders and pre-procedurally matched closing devices based on 3D-printed models.

Conclusions

3D-printing from 3D-TEE is technically feasible. Both shape and location of PVLs are preserved during model preparation and printing. It remains to be tested whether 3D printing would improve outcomes of percutaneous PVL closure.

Procedural Tools and Technics for Transcatheter Paravalvular Leak Closure: Lessons from a Decade of Experience

Prosthetic paravalvular leaks (PVLs) are associated with congestive heart failure and hemolysis. Surgical PVL closure carries high risks. Transcatheter implantation of occluding devices in PVL is a lower risk but challenging procedure. Of the available devices, only two have been specifically approved in Europe for transcatheter PVL closure (tPVLc): the Occlutech^® Paravalvular Leak Device (PLD) and Amplatzer™ ParaValvular Plug 3 (AVP 3). Here, we review the various tools and devices used for tPVLc, based on three observational registries including 748 tPVLc procedures performed in 2005-2021 at 33 centres in 11 countries. In this case, 12 registry investigators with over 20 tPVLc procedures each described their practical tips and tricks regarding imaging, approaches, delivery systems, and devices. They considered three-dimensional echocardiography to be the cornerstone of PVL assessment and procedure guidance. Anterograde trans-septal mitral valve and retrograde aortic approaches were used in most centres, although some investigators preferred the transapical approach. Hydrophilic-coated low-profile sheaths were used most often for device deployment. The AVP 3 and PLD devices were chosen for 89.0% of procedures. Further advances in design and materials are awaited. These complex procedures require considerable expertise, and experience accumulated over a decade has no doubt contributed to improve practices.

Three-dimensional printed moulds to obtain silicone hearts with congenital defects for paediatric heart-surgeon training

OBJECTIVES

Many types of congenital heart disease are amenable to surgical repair or palliation. The procedures are often challenging and require specific surgical training, with limited real-life exposure and often costly simulation options. Our objective was to create realistic and affordable 3D simulation models of the heart and vessels to improve training.

METHODS

We created moulded vessel models using several materials, to identify the material that best replicated human vascular tissue. This material was then used to make more vessels to train residents in cannulation procedures. Magnetic resonance imaging views of a 23-month-old patient with double-outlet right ventricle were segmented using free open-source software. Re-usable moulds produced by 3D printing served to create a silicone model of the heart, with the same material as the vessels, which was used by a heart surgeon to simulate a Rastelli procedure.

RESULTS

The best material was a soft elastic silicone (Shore A hardness 8). Training on the vessel models decreased the residents' procedural time and improved their grades on a performance rating scale. The surgeon evaluated the moulded heart model as realistic and was able to perform the Rastelli procedure on it. Even if the valves were poorly represented, it was found to be useful for preintervention training.

CONCLUSIONS

By using free segmentation software, a relatively low-cost silicone and a technique based on re-usable moulds, the cost of obtaining heart models suitable for training in congenital heart defect surgery can be substantially decreased.